Polyols based on regenerable raw materials, such as fatty acid triglycerides, sugar, sorbitol, glycerol and dimer fatty alcohols, are already used in diverse ways including as a raw material in the preparation of polyurethane materials. The use of such components will increase further in the future, because products made from renewable sources are rated advantageously in ecobalances and the availability of petrochemical-based raw materials will decrease in the long term.
An increased use of sugar, glycerol and sorbitol as well as oligo- or polysaccharides as the polyol component in polyurethane formulations on the one hand is complicated by their low solubility in or high incompatibility with other polyether or polyester polyols often employed in polyurethane chemistry, and on the other hand these substances impart adversely high OH numbers to the polyol component, even when employed in low amounts, because of their high density of hydroxyl groups.
Fatty acid triglycerides are obtained in a large amount from regenerable sources and therefore form an inexpensive basis for polyurethane raw materials. In rigid foam formulations specifically, this class of compound is distinguished by a high dissolving capacity for physical blowing agents based on hydrocarbons. A disadvantage is that only few fatty acid triglycerides have the reactive hydrogen atoms necessary for the reaction with isocyanates. Exceptions are castor oil and the rare lesquerella oil. However, the availability of castor oil is limited due to spatially restricted cultivation areas.
A further problem in the use of triglycerides in foam formulations is their incompatibility with other polyol components, in particular with polyether polyols.
Quite a number of workers in the art have proposed solutions to the problems described hereinabove.
DE-A 33 23 880 and WO 2004/20497 are concerned with the use of double metal cyanide complex catalysts in the preparation of alkylene oxide adducts based on starter components from regenerable sources with the aim of rendering these accessible to polyurethane chemistry. Castor oil is often employed as the preferred starter component, and oils modified subsequently with hydroxyl groups can also be used. According to the processes described, only relatively high molecular weight polyether polyols are accessible, and furthermore the triglycerides used, if castor oil is not employed, must be modified with hydroxyl groups in a separate reaction step.
According to U.S. Pat. No. 6,420,443, compatibilizers for blowing agents based on hydrocarbons are obtained by addition of alkylene oxide on to hydroxylated triglycerides. In a similar manner, DE-A 101 38 132 describes the use of OH adducts of castor oil or hydroxylated fatty acid compounds and alkylene oxides as hydrophobizing components in very flexible polyurethane systems.
The teaching of U.S. Pat. No. 6,686,435, EP-A 259 722, U.S. Pat. No. 6,548,609, US-A 2003/88054, U.S. Pat. No. 6,107,433, DE-A 36 30 624, U.S. Pat. No. 2,752,376, U.S. Pat. No. 6,686,435 and WO 91/05759 is ring-opening of epoxidized fatty acid derivatives and the use of the products obtained in polyurethane systems.
WO 2004/96744 discloses a process for the hydroxylation and hydroxymethylation of unsaturated fatty acid esters, further reaction thereof by transesterification to give branched condensates being the teaching in WO 2004/96882. The use of these condensates containing OH groups in flexible foam formulations can be seen from WO 2004/096883.
U.S. Pat. No. 6,359,022 discloses transesterification products of hydrophobic components, e.g. triglycerides, phthalic acid derivatives and polyols, as the OH component in rigid foam formulations which use alkanes as blowing agents. The polyether polyols optionally additionally employed in the polyol component must be prepared in a separate reaction step. EP-A 905 158 discloses blowing agent emulsifying aids for rigid foam formulations based on esterification or transesterification products of fatty acid derivatives and alcohols. The teaching of EP-A 610 714 is the preparation of hydrophobic rigid polyurethane foams by co-using esterification products of OH-functional fatty acid derivatives with low molecular weight polyols.
WO 200640333 and WO 200640335 disclose hydrophobically modified polysaccharides which are obtained by esterification with fatty acids, and the use thereof as components which increase the compressive strength in flexible foam formulations.
DE-A 196 04 177 describes the transesterification of castor oil or hydroxylated triglycerides with alkylene oxide addition products of polyfunctional starter alcohols and the use thereof as storage-stable components in the preparation of massive systems which cure without bubbles.
The teaching of DE-A 199 36 481 is the use of long-chain castor oil polyether-ols as components for the preparation of soundproofing flexible foams. The conditions of the preparation of the castor oil polyether-ols are not dealt with concretely.
DE-A 198 12 174 discloses the reaction of transesterification products of polyfunctional alcohols and triglycerides with alkylene oxides, and the transesterification of prefabricated polyether polyols with triglycerides in two-stage processes. According to the teaching of DE-A 198 12 174, it is also possible to interrupt the transesterification reaction, to add alkylene oxide, and then to continue the transesterification reaction. In DE-A 198 12 174, reaction conditions are employed in the preparation of the alkylene oxide addition products which lead to usable products only in the very specific cases described there by way of example; also, the alkaline polymers obtained are not worked up, as a result of which their usability is severely restricted further.